An air conditioner includes a motor for a refrigerant compressor, and a power converter for supplying desired power to the motor. A common power converter includes a converter, an inverter, and a smoothing capacitor between them, and converts power supplied from an alternating-current power supply. Also, a reactor is provided to improve the input power factor. For example, the inductance of the reactor is about 2 mH, and the capacitance of the capacitor is about 2000 μF.
The reactor and capacitor are especially large-sized and heavy-weighted among the parts of the power converter. Also, they constitute a cause of increased loss due to heat generation.
Accordingly, a technique is proposed in which the capacitance of the capacitor is reduced to downsize the capacitor. This technique is commonly called “capacitor-less”.
Techniques related to the present invention are shown below. Particularly, Non-Patent Document 3 discloses a technique that further omits the reactor.
Non-Patent Document 1: Myint Ko Tun and one other, “New Type Sinusoidal Input UPS Controlled by DC Chopper Type Active Filter”, the Transactions III of Heisei 14 (2002) IEEJ Industry Applications Society Conference, The Institute of Electrical Engineers of Japan, August Heisei 14 (2002), pp. 1301-1306
Non-Patent Document 2: Yoichi Ito and one other, “Capacitor-less PWM Inverter”, The transactions of Showa 63 (1988) IEEJ Industry Applications Society National Conference, The Institute of Electrical Engineers of Japan, August Showa 63 (1988), pp. 445-450
Non-Patent Document 3: Hitoshi Haga and one other, “Method of Improving Input Current Waveform of Single-Phase Field Capacitor-less IPM Motor Driving Inverter”, The Transactions I of Heisei 14 (2002) IEEJ Industry Applications Society Conference, August Heisei 14 (2002), pp. 415-418